Method of forming flat bottoms on bags of creasable material

ABSTRACT

This disclosure concerns a method for forming a flat bottom on a bag of flat tubular stock comprising a material which, when folded and pressed, is left with somewhat permanent creases. To practice the method, an unfinished bag is provided in the form of a section of the tubular stock flattened in a manner to provide opposite longitudinally-extending laterally-inwardly-folded pleats with the bag completely sealed across one end and being openable at the other end. Assuming the flattened bag in a generally horizontal plane, the upper edges of the pleats are gripped while the lower edges are held fast at areas of the bag spaced from the sealed end thereof at a distance equalling twice the depth of the pleats. Thereafter, the gripped areas are pulled toward the openable end to drag the intended flat bottom portion longitudinally over the underlying bag portion until taut. Then, the intended bottom portion is pressed against the underlying portion to form creases in the bag outlining its flat bottom.

1 June 3, 1975 1 METHOD OF FORMING FLAT BOTTOMS ()N BAGS OF CREASABLEMATERIAL John B. Cole. Bratenahl. Ohio [73] Assignee: Midland-RossCorporation.

Cleveland. Ohio 1 Filed: May 23. 1973 211 Appl.No.:362.888

[75] Inventor:

[521 LES. Cl 93/35 SB: 93/84 FF: 93/84 TW [51] Int. Cl B3lb 33/26 [58]Field of Search 93/35 SB. 35 R. 84 FF. 93/84 R. 84 TW, 31. 27

[56] References Cited UNITED STATES PATENTS 3.094905 (1,1963 Haslacher.93/35 SB 3.329.260, 7/1967 Medleycott 93/84 FF 3.554.099 l/l97l Rodley..93/27 X 3.606.821 9/1971 Plat7. et al. 93/35 SB Primary E.\'aminer-RoyLake Assistant l;'.\'aminer-.lames F. Coan Attorney. Agent. orFirmWoodrow Portz l 5 7 1 ABSTRACT This disclosure concerns a method forforming a flat bottom on a bag of flat .tubular stock comprising amaterial which. when folded and pressed. is left with somewhat permanentcreases. To practice the method, an unfinished bag is provided in theform of a section of the tubular stock flattened in a manner to provideopposite longitudinally-extending laterally-inwardlyfolded pleats withthe bag completely sealed across one end and being openable at the otherend Assuming the flattened bag in a generally horizontal plane, theupper edges of the pleats are gripped while the lower edges are heldfast at areas of the bag spaced from the sealed end thereof at adistance equalling twice the depth of the pleats. Thereafter, thegripped areas are pulled toward the openable end to drag the intendedflat bottom portion longitudinally over the underlying bag portion untiltaut. Then. the intended bottom portion is pressed against theunderlying portion to form creases in the bag outlining its flat bottom.

1 Claim, 15 Drawing Figures METHOD OF FORMING FLAT BOTTOMS ON BAGS OFCREASABLE MATERIAL BACKGROUND OF THE INVENTION In the use of bagsprovided in a flat condition, e.g., at the checkout counters ofsupermarkets, it is desirable to be able to-unfold the bag from its flatcondition into a box-like configuration and have the bag stand on itsflat bottom in a self-supporting condition while merchandise is packedthereinto. Paper bags perform admirably in this respect but are subjectto tearing on being exposed to any dampness as from rain, or wet foodproducts.

Bags of plastic film offer great advantage in strength and weatherresistance over the conventional paper bags in, e.g., food retailing,but have not been accepted because of a lack of rigidity whichfacilitates opening, handling, and self-support incidental to theplacing of packages therein. While present experimental work indicatesthat the problem of film rigidity may be solved by the coextrusion offilms having laminae of different densities, plastic films are not idealfor bag formation by methods used for paper bags.

According to present technology, a plastic bag may be formed mostefficiently from a tube divided longitudinally into sections of whicheach is sealed across one end. Then the difficulty arises of bringingthe resulting semi-finished bag into a desirable commercial form whereinit may be manually shaken into an open condition providing a flat bottomby which it can be seated and be self-supporting on a flat surface.Method and apparatus for forming a flat bottom to a pleated bag areknown, e.g., from US. Pat. No. 3,606,822. In developing the presentinvention it has been discovered that a pleated tube section may beshaped with a flat bottom by simpler method and apparatus thanheretofore known to the present inventor.

It is an object of this invention to provide a method for forming flatbottoms on flattened bag stock for which machinery may be readilydesigned to -perform in a rapid manner on a series of such bagsproceeding through a bag bottom shaping station.

An object ancillary to the above object is to provide a method thatinvolves a minimum of manipulation of the bag material in shaping theflat bottom and advantageously utilizes a flattened air evacuatedcondition of bag sections as normally provided from machinery forprocessing a bag-making tubular material.

It is particularly an object to render plastic bag materials more usefuland commercially practical in the retail merchandising fields.

In fulfilling these and other objects, the invention resides in a methodof producing bags with flat bottoms from a creasable material, e.g., aplastic film comprising laminae of diverse compositions, in the form ofa flattened tube having longitudinally extending pleats folded laterallyinwardly to a predetermined depth. Assuming a semi-finished bag sectionhaving one end sealed along a transverse seal line and the other endopenable to be oriented in a generally horizontal plane, each pleatforms two superimposed edges one above the other. To form the flatbottom, the bag is supported on a flat surface in a substantiallydeflated condition and the lower edges of both pleats next to thesurface. In a fold plane located from the seal line at a distance equalto twice the depth of either pleat, the lower edges of the pleats aresecured to prevent movement relative to the flat surface, and both upperedges of the pleats are gripped in a manner to maintain the materialbetween the gripped areas in taut condition while the means for grippingis advanced toward the openable end to drag the taut material over thenow underlying areas of the bag between said held lower edges until thelongitudinally overlying advanced portion of the bag which consequentlynow extends between the gripped areas and the fold plane has a length oftwice the depth of the pleats and assumes a taut condition. Theoverlying advanced bag portion is then pressed at sufficient pressureand/or temperature against the underlying bag portion to develop creasesor fold lines which define and outline the flat bottom of the bag.

The holding of the bag to the flat surface and the gripping of the upperedges is carried out with merely such means as are necessary to provideadequate gripping of the areas involved without slipping and may consistof very thin members which may pass by each other without interferencesubstantially changing the height of the flattened bag. The portion ofthe bag which is advanced toward the openable end is preferably liftedonly slightly with respect to the underlying portion to pass thereoverin light frictional contact. This is preferable since, to raise theadvanced portion to any considerable degree would tend to introduce airinto the portions of the bag undergoing relative movement and cause anundesirable crease pattern of the bag as a result of the bottom pressingoperation. The advancement of the bottom forming portion of the bag ispreferably done with as complete deflation of the bag material aspossible.

According to one embodiment disclosed, gripping elements may be employedto grip the upper pleat edges on the side of the above indicated foldplane nearer the seal line and rotate it about on an axis approximatelythrough its edge further from the fold line before or during advancementtoward the openable end of the bag.

In the drawing with respect to which the invention is described:

FIG. 1 is a fragmentary perspective view of a bag being subjected toedge separation of its lateral pleats;

FIG. 2 is a cross sectional view of the bag shown in FIG. 1 as takenalong plane A-A;

FIGS. 3 and 4 are fragmentary perspective and transverse cross sectionalviews respectively illustrating means for gripping the upper edges andmeans for holding the lower edges to a support in place before anyrelative longitudinal movement of bag portions has taken place;

FIGS. 5 and 6 are fragmentary perspective and longitudinal-diagrammaticviews of a bag in association with apparatus having partially effectedlongitudinal shifting of the bottom forming bag portion relative torestrained portions of the bag;

FIGS. 7 and 8 are fragmentary perspective and diagrammatic-longitudinalelevation views respectively of the bag at completion of the bottomportion advancing stroke with gripping and holding means still in place;

FIGS. 9 and 10 are fragmentary diagrammatic elevation views of twostages of a pressing elevation and apparatus therefor;

FIGS. 11 14 are fragmentary diagrammatic elevation views of a modifiedprocess wherein the means for gripping the upper pleat edges of the bagmay be rotated through 180 at the beginning, or during, the advancementof the bottom portion of a bag to the position for being pressed; and

FIG. 15 is a perspective view of the bag of the other figures inexpanded self-supporting condition.

DESCRIPTION OF PREFERRED EMBODIMENT FIG. 1 illustrates a bag 5 restingin flattened condition on a support 6, such as a section of an endlessconveyor belt. The bag 5 typically originates as a section of acontinuously extruded tube of fiIm. The tube, after leaving an extruder,passes through machinery not shown for flattening the tube and forminglongitudinal pleats 7a,7b therein as shown in FIG. 2 as taken in crosssection along plane A-A of FIG. 1. The bag 5 is open along end 8 butclosed along end 9 by a seal line 10 along which all opposing surfacesof the bag including those of the pleats are sealed together. Assumingthe bag to be flattened in a horizontal plane, it has upper edges 14,15formed by the pleats and lower pleat edges 16,17 normally locatedagainst a flat surface such as that provided by the upper face of thesupport 6. FIGS. 1 and 2 illustrate air jets 18,19 which project air orother gas against the pleat edges to separate the upper edges 14,15 fromthe lower edges 16,17 in preparation for being engaged by grippingdevices 21,22/ Fingers or clamp elements 21a,21b of device 21 grip oneupper pleat edge 14 while fingers 22a,22b of device 22 grip the otherupper edge 15. It should be noted that devices 21,22 grip areas of thebag on the side of plane AA or its line 24 of intersection with the bagthat is nearer the seal line 10.

The bag 5 is held fast to the support 6 by fingers or clamp elements25,26 which engage the upper sides of lower pleat edges 16,17 17respectively and hold the bag against any movement relative to thesupport 6 during subsequent longitudinal shifting of the bottom formingarea toward the openable end 8 of the bag. As shown in FIG. 3, the area28 between line 24 and the end 9 of the bag constitutes about one-halfof the bottom portion 30 of the bag as shown in FIG. 7 with the otherhalf portion 29. The extreme end 9 of the bag as shown in FIG. 3 isshown located between bottom halves 28,29 in FIG. 7.

In FIG. 4, the support 6 is shown perforated to provide openings 31which permit communication between the vacuum chamber 32 and theunderside of the bag 5. The vacuum force or negative pressure applied tothe underside of the bag 5 is in any case helpful in holding the bag inposition while performing the bottom shaping opration. However, it ispossible with sufficient vacuum force applied to the underside of thebag 5 in a selective manner to eliminate the fingers 25,26 as means forsecuring the bag to the support 6. As FIG. 4 illustrates, the fingers25,26 are carried on devices 34,35, each of which comprises fluidcylinders 36,37 connected in right-angle series relationship with thefluid cylinder 37 directly supporting the fingrs or 26.

FIGS. 5 and 6 illustrate an intermediate stage of traversing the bottomportion of the bag comprising areas 28,29 toward the openable end 8 ofthe bag.

FIGS. 7 and 8 illustrate the bottom portion of the bag 5 completelyadvanced toward the openable end 8 with the bottom portion of the bag ina taut condition longitudinally as well as transversely.

As shown in FIG. 2, the devices 21,22 comprise fluid cylinders 38,39connected in series-angle relationship to effect both lateral andvertical movements of jaws 21b,22b. Jaws 21a,22a are fixed with respectto the fluid cylinders 39 whereas jaws 21b,22b are moved by respectivefluid cylinders 39 to effect clamping of the upper pleat edges 14,15.During gripped condition of the edges 14,15, the cylinders--38 areoperable to shift each pair of fingers in a lateral outward direction toproduce lateral tautness in the intervening wall of the bag. The devices21,22 are shown movably supported on tracks 41,42 which extend parallelto the Iongitudinal direction of the bag 5 or the support 6. Mechanicalmeans in variety are known for transversing the devices 21,22longitudinally of the tracks 41,42 to accomplish any desired motion ofthe devices 21,22 in shifting the bottom bag portion comprising areas28,29 from the condition of FIG. 3 to that of FIG. 7. Also readilyavailable is controlling apparatus with cycling and timing mechanismsfor programming the various power elements such as fluid cylinders36,37,38,39 and means for propelling the devices 21,22 along tracks41,42 to effect any desired movements of fingers or clamping components,such as described above for gripping and holding the bag 5.

Such apparatus will also cause release of such bag grippers at a properinstant during a pressing operation as illustrated in FIGS. 9 and 10.These figures illustrate an apparatus which may be used to press thebottom portion 30 of the bag. Schematically shown is a press unit 45capable of movement in the direction of the arrows perpendicular to theplane of the bag 5 which comprises, e.g., a pair of plates 46,47 hingedtogether at an axis 48 with the other ends of the plates pivotallysupported on lower slotted extensions 51,52 of the body 53. The plates46,47 may be equipped with electrical cartridge heaters 49 as shown toheat the plastic material of the bag in promoting crease permanence.This construction allows hinged portions of the plates disposedcentrally under the body 53 to sag downward and first contact a middlearea of the bag bottom 30 in a pressing operation.

As the press member 45 is lowered and establishes engagement with thebag bottom, the holding clamps 25,26 and the gripping clamps 21a,2lb,22a,22b may be withdrawn as the pressing member while descending firstengages the bag to prevent any relative movement of portions thereof andthen further descends to the position of FIG. 10 wherein the plates46,47 assume a planate condition and effect such pressing of the bag asto form somewhat permanent creases which outline and define the bottomarea of the bag. The bag is now formed with the bottom area 30 and maybe jerked out into its box configuration as shown in FIG. 15 and be selfsupporting on its bottom 30.

FIGS. 1 1 14 illustrate a mode of practicing the present inventionwherein the bag is manipulated in a slightly different manner to achieveformation of the bottom 30 of FIG. 14. In this latter embodiment, thebag 5 may be secured or held to the support 6 by fingers 25,26 aseffected in the earlier described embodiment. The upper pleat edges aregripped by two pairs of elements somewhat in the manner effected bydevices 25 and 26, as shown in FIG. 3, but at a different location withrespect to the fold line plane AA. As shown, a pair of clamp elements orfingers 61,62 are shown gripping the upper pleat edge 14 immediatelyadjacent to the plane but on the side thereof nearer its open end andaway from the closed end 9. It will be noted that the upper half of thebottom surface 28 extends from the plane A to the closed end of the bag9.

As FIG. 12 indicates, the elements 61,62 may rotate together about anaxis extending transversely of the bag 5 adjacent and parallel to theedges 61a,62a of the elements which were initially toward the openableend of the bag from the plane AA, as shown in FIG. 13, but face towardthe closed end of the bag after rotation as shown in FIG. 13 orcompletion of the advancement of the bottom portion of the bag towardthe openable end as shown in FIG. 14. The rotation of the elements 61,62may occur without appreciable advancement toward the open end of thebag, or occur during the advancement of the elements toward the positionof FIG. 14 by suitable apparatus. The bottom 30 may be pressed as shownin FIGS. 9 and to obtain a suitable crease pattern for maintaining thebag in an expanded condition as shown in FIG. 15.

I claim:

1. A method of producing a bag with a flat bottom from a bag-formingmaterial provided as a flattened tube having symmetrically oppositelongitudinally extending pleats folded laterally inwardly to a uniformpredetermined depth to provide two superimposed edges at each side ofthe tube, said edges occurring as two laterally opposite upper edges andtwo laterally opposite lower edges when said flattened tube assumes ahorizontal planate position, comprising the steps of:

' providing in the form of a bag a section of said flattened tubecontinuously sealed in a straight seal line across one end of the bag,to band together all adjacent surfaces including those of said pleats,the other end of the bag being freely openable;

supporting said bag substantially in a plane on a flat surface with saidlower edges next to said surface in a flat substantially deflatedcondition;

with reference to a fold plane in transverse perpendicular relation tothe general plane of the bag located at an approximate distance fromsaid seal line equal to twice the depth of either of said pleats, saidplane having a near side and a far side in reference to said seal line,holding both lower edges at locations along said far side injuxtaposition to said plane in fixed adjacent relation to the plane ofsaid flat surface;

gripping both upper edges along areas in juxtaposirotating a meansgripping said areas about its far side before completing its movement toplace said longitudinally advanced portion of the bag in a tautcondition; and

pressing the entire advanced bag portion against the underlying bagportion to develop fold lines which define and outline said flat bottom.

1. A method of producing a bag with a flat bottom from a bagformingmaterial provided as a flattened tube having symmetrically oppositelongitudinally extending pleats folded laterally inwardly to a uniformpredetermined depth to provide two superimposed edges at each side ofthe tube, said edges occurring as two laterally opposite upper edges andtwo laterally opposite lower edges when said flattened tube assumes ahorizontal planate position, comprising the steps of: providing in theform of a bag a section of said flattened tube continuously sealed in astraight seal line across one end of the bag, to band together alladjacent surfaces including those of said pleats, the other end of thebag being freely openable; supporting said bag substantially in a planeon a flat surface with said lower edges next to said surface in a flatsubstantially deflated condition; with reference to a fold plane intransverse perpendicular relation to the general plane of the baglocated at an approximate distance from said seal line equal to twicethe depth of either of said pleats, said plane having a near side and afar side in reference to said seal line, holding both lower edges atlocations along said far side in juxtaposition to said plane in fixedadjacent relation to the plane of said flat surface; gripping both upperedges along areas in juxtaposition to, and on the far side of, saidplane in a manner maintaining said material between the gripped areas intaut condition, and advancing said gripped upper edges with the tautmaterial therebetween over said held areas of the lower edges and otherintermediate bag surface in close to slidable relation therewith towardsaid openable end to bring a longitudinally advanced portion of the bagtheretofore extending between fold line and the gripped areas measuringtwice said pleat depth into a taut condition; rotating a means grippingsaid areas about its far side before completing its movement to placesaid longitudinally advanced portion of the bag in a taut condition; andpressing the entire advanced bag portion against the underlying bagportion to develop fold lines which define and outline said flat bottom.